The present invention relates to a suction system for a fuel-air mixture to an inlet valve of a reciprocating piston internal combustion engine with a check valve in the suction line, an externally actuatable closure valve for the suction line and an injection nozzle.
Such a valve system is disclosed in the DE-OS No. 24 19 295. The suction line is closed at lower rotational speeds of the internal combustion engine, i.e., at low air velocities of the suction air by a rotatable closure valve. Within this rotational speed range, the air inlet takes place exclusively by way of a leaf spring valve installed into the closure valve and acting as check valve which is lifted off by the inflowing air from its valve seat and opens up a through-flow opening in the closure valve. In case of a return flow of the air, the leaf spring valve closes. It can thus be avoided that a part of the mixture introduced into the cylinder can be pushed back during the compression stroke into the suction line through the still open inlet valve and the filling of the cylinders is deteriorated thereby. In order to avoid an excessive throttling of the suction air at increasing rotational speeds, provision is made to rotate the closure valve into the open position by the throttle valve pivotally connected therewith. As only a relatively small opening cross section can be accommodated in the closure valve, the throttling nonetheless becomes relatively high so that the closure valve has to be opened already at rotational speeds at which a return flow of the sucked-in fuel/air mixture may still take place.
It is therefore the object of the present invention to provide a constructively simple and compact suction system in which the closure valve has to be opened only at higher rotational speeds of the internal combustion engine.
The underlying problems are solved according to the present invention in that the check valve is installed into a by-pass line by-passing the closure valve. If one installs the check valve into a by-pass line with respect to the closure valve, one is not limited by the size of the closure valve in dimensioning the through-flow cross section of the check valve. The through-flow cross section of the check valve can be dimensioned as large as the free cross section of the suction line so that the throttle losses can be reduced.
A particularly advantageous spatial arrangement results if the by-pass line consists of windows of the suction line covered off externally by spring lamellae and of bores adjoining the windows and extending at an acute angle to the suction line. In this case, nearly the entire circumferential surface of the suction line can be utilized as through-flow cross section. The by-pass flow of the closure valve branches off symmetrically upsream of the closure valve and terminates downstream thereof in the suction line so that no reason exists for a turbulence conditioned by asymmetry. A good mixing of the sucked-in air with fuel is served by this measure of arranging the injection nozzle at the suction line with the same angle as the bores of the by-pass lines so that its jet meets with the air bores of the by-pass line along the longitudinal axis of the suction line.